1. Field of the Invention
The present invention relates to a welding quality decision apparatus and a welding machine provided with the same apparatus for judging quality of a joint portion welded by, for example, a flash welding machine.
2. Description of the Related Art
FIG. 6 is a view showing a cut shape measurement apparatus to be used after flash trimming and disclosed in FIG. 3 of Japanese Examined Utility Model Publication No. 58-35372.
According to this publication, a laser beam is generated from ,a laser oscillator 104, a slit-like laser beam 106 is produced by a beam expander lens 105, and the laser beam 106 is irradiated onto a flash-trimmed welding joint 103 which is a substance to be measured.
When the weld joint 103 is subjected to the excessive or insufficient cut, a bumpy surface of the weld joint 103 results. The reflective light of the laser beam 106 becomes a ray of light of an uneven intensity. The reflective light is picked up by a television camera 107 and displayed on a monitor television set 108. The excessive or insufficient amount of cut is digitalized by a signal processing circuit 109 and a YES/NO decision circuit 110 where it is judged whether or not the amount is in the allowance range. In the case where the amount is out of the allowance range, an alarm signal is issued from an alarm 111.
Such a cut shape measurement apparatus is used not to make a decision of the welding quality but to measure the shape of the trimmed weld flash.
Also, the structure of a conventional flash welding machine is shown in, for example, Japanese Examined Patent Publication No. Hei 5-23877. This is shown in FIGS. 7 and 8.
In the shown machine, the welding machine and a trimmer are disposed in the same area, and the welding joint is trimmed after a steel plate has been flash welded while it is being clamped by electrodes.
In FIGS. 7 and 8, reference numerals 1 and 2 denote metal strips, reference numeral 3 denotes a common base, reference numeral 4 denote a stationary frame fixed to the common base 3, and reference numerals 5 and 6 denote upper and lower electrodes on the stationary side provided on the stationary frame 4. Reference numerals 7 and 8 denote upper and lower electrodes on the movable side provided on a movable frame 16, reference numeral 9 denotes a stationary-side rotary shear, 10 denotes a movable-side rotary shear, and reference numeral 11 denotes an upper trimmer cutting tool unit.
When the leading metal strip 1 stops at a predetermined position within the welding machine, the metal strip 1 is clamped and maintained by the stationary side upper and lower electrodes 5 and 6 and an auxiliary clamp.
Subsequently, the trailing metal strip 2 stops at a predetermined position within the welding machine, the metal strip 2 is clamped by the movable side upper and lower electrodes 7 and 8.
Thereafter, the rotary shears 9 and 10 positionally selected in the strip delivery direction from the rear side are advanced to cut each end of the strips 1 and 2.
When the end faces are thus refined, the movable frame 16 is advanced to abut the ends of the strips with each other. The flash weld is performed under the condition that the ends are in abutment with each other.
After the completion of the welding, under this condition without any change, the trimmer cutting tool unit 11 is advanced to complete the trimming operation.
In this welding machine, since the trimming operation is performed under the condition that the steel plates are clamped by the electrodes, when the trimming operation is being performed, the distance between the inlet side electrode frame and the outlet side electrode frame is very short. Accordingly, it is very difficult to perform the decision of the welding quality of the welding joint lay viewing. For this reason, the decision of the welding quality is made by the visual inspection after the welding joint port has been fed out of the welding machine.
However, in this method, when the welding fault is found it is necessary to return the steel plates back to the welding position within the welding machine in order to re-weld the part. Accordingly, the mechanism therefor is needed and at the same time, a remarkable time loss is caused to degrade the work efficiency.
Also, due to the visual inspection, it is impossible to quantitatively express the decision of the welding quality. The evaluation must depend upon the experience of the individual operator.
Also, the system suffers another problem that the rewelding must be performed manually.
In order to obtain the excellent welding quality, upon the welding operation, for example, upon the flashing operation, it is necessary to sufficiently heat the welding joint. If this heat is insufficient, it is impossible to perform the sufficient preparation, resulting in welding fault while impurities such as oxidant are left in the welding joint. Namely, it is one of the important factors for representing the welding quality to monitor the amount of the applied heat.
However, since it is difficult to directly measure the amount of applied heat itself, an object of the present invention is to provide a welding machine and an apparatus for performing the rewelding, in which the measurement of the amount of heat is indirectly measured by measuring a temperature, a color, a luster or the like of a member to be welded, such as the welding joint of the steel plate after welding so that on the basis of this, the quantitative decision of the welding quality is made and the rewelding operation can be automatically performed in case of the welding fault. Also, in addition, an object of the present invention is to overcome the above-described problems.